The invention relates to the use of timing reference with devices which accept such signals provided from an internal or external source. The invention is of particular use in television systems where it is frequently desired to provide video delays which may be automatically or operator adjusted from time to time while at the same time maintaining synchronization of an associated audio or other signal. Other uses and purposes for the present invention will also become known to one skilled in the art from the teachings herein.
1. Field of the Invention
The field of the invention includes the use of timing reference signals having particularly long sequences as related to their shortest transition. Various devices accept such signals provided from an internal or external sources and operate to adjust their internal mechanisms accordingly. It is frequently desired to provide adjustment of such timing reference signals.
2. Description of the Prior Art
It is well known in television systems to provide for timing adjustment of the television signal by distributing a common timing reference comprised of one or more signals throughout the facility. This timing signal is frequently called black burst and color black. Each video processing device in the facility receives this timing reference, operating to output its video signal in synchronism with this reference. Frequently, it is desirable to have some adjustment in the phase between the output video signal and the reference signal and this adjustment is provided within the video processing device. These adjustable delays typically are limited in range, with the largest limited to around 3 horizontal lines (.apprxeq.200 .mu.s). It is also known to provide adjustable delays for video by means of switched analog or digital delay lines. As with the devices above, this adjustment if limited in range. Additionally, it is known to provide automatically adjustable delays of video signals in Time Base Corrector and Video Frame Synchronizer devices such as described in U.S. Pat. Nos. 3,860,952 and 4,018,990. These devices digitize an incoming video signal according to the sync thereon, store the digitized video into a memory and read the stored video out of memory according to the reference signal. A limited amount of operator adjustment is frequently provided to allow phase variations to be introduced between the output video signal and the reference in order to accommodate delays to the video signal elsewhere in the facility, such as delays due to cabling. Normally, the above described adjustments in phase between the reference and the output video signal are operator type and require some skill and specialized procedures for the operator to perform, thus making frequent adjustment difficult. In addition, due to the relatively small adjustment range provided by the equipment, there are limitations on the amount of external delay which can be accommodated by operator adjustment.